1. Field of the Invention
The present invention relates to a liquid discharge head that ejects liquid, such as ink, and a recording apparatus having the same.
2. Description of the Related Art
A known example of a liquid discharge head is an inkjet recording head (hereinafter referred to as a recording head). The recording head is provided with a recording element substrate for ejecting liquid such as ink. Recording is performed such that ink held and stored in an ink tank is supplied to the recording element substrate through an ink supply channel.
In a color printer that uses more than one kind of ink, a recording element substrate to which the more than one kind of ink is supplied is mounted to a recording head. As printers are increasingly dropping in price in recent years, efforts are being made to reduce the areas of, particularly, the high-cost recording element substrates. 
As shown in FIG. 12, a recording element substrate H1101 has a plurality of discharge port arrays H1108 (one discharge port group corresponding to one ink supply port is defined as one discharge port array) at predetermined intervals. An increase in cost due to an increase in the area of a recording element substrate is prevented by decreasing the distance between the discharge port arrays (between colors). Ink supply ports H1102 are formed in correspondence with the discharge port arrays H1108, respectively.
A flow of ink until it is supplied to ink supply ports formed in a recording element substrate will be described using an example in which a recording head is integrally provided with an ink tank for holding and storing ink. FIG. 14A shows an external view of an ink-tank integral-type recording head disclosed in U.S. Patent Laid-Open No. 2005-0285904, and FIG. 14B shows the internal structure thereof.
As shown in FIG. 14B, an ink-tank integral-type recording head H1000 capable of supplying more than one kind of ink includes a plurality of ink containing portions H2001 to H2003 for holding ink. FIGS. 15A and 15B are sectional views of the recording head H1000, and FIGS. 16A to 16C are diagrams for describing the shape of an ink supply path.
To describe the shape of an ink supply path S01  among ink supply paths S01 to S03 shown in FIG. 16B, FIG. 15A shows a perspective view of a section of an ink tank H1500 cut along the ink supply path S01; FIG. 15B shows an enlarged view of a part XVB of the perspective sectional view. As shown in FIGS. 15A and 15B, ink contained in the ink containing portion H2001 passes through an ink introduction passage H2101 through a filter H1701 and passes through a liquid chamber H2201 to reach the ink supply port H1102. Thus, a plurality of discharge ports is equally supplied with ink from the liquid chambers. As shown in FIG. 16A, “an ink supply path” in this specification indicates a part constituted by “an ink introduction passage” serving as a liquid introduction passage and “a liquid chamber”, and the connecting portion between the ink introduction passage and the liquid chamber is referred to as a communicating portion C.
The relationship between the recording element substrate and the ink supply path will be described herein. As described with reference to FIG. 12, the recording element substrate H1101 is provided with the ink supply ports H1102 corresponding to the individual discharge port arrays H1108. FIG. 16B is a diagram showing the ink supply paths S01 to S02 and the recording element substrate H1101 corresponding to the recording head H1000. As shown in FIG. 16B, liquid chambers H2201 to H2203 which are part of the  individual ink supply paths S01 to S03 are arranged parallel in correspondence with the individual ink supply ports H1102. Accordingly, as shown in FIG. 16C, the liquid-chamber width W of at least the inner ink supply path S01 is generally set, at about 0.6 to 0.8 mm, in agreement with the width W′ of the ink supply port H1102 (see FIG. 12) because the distances between the individual colors are short.
Meanwhile, it is known that ink in ink supply paths or the like contains gas (dissolved gas) dissolved in the ink and external gas that passes through an ink tank formed from polymer or the like. If these gases are turned into bubbles in liquid chambers, the bubbles sometimes remain in the liquid chambers for a long time until the bubbles pass into the ink introduction passages that are wider in the y-direction than the liquid chambers or are sometimes left in the liquid chambers. This is because bubbles hardly move in the liquid chambers because the liquid-chamber width W is small. Thus, if bubbles remain or are left in the liquid chambers for a long time, they can exert a bad influence on recording.
In this case, the bubbles are generally removed by, for example, joining a member called a cap to the discharge-port formed surface of a recording head, and reducing the pressure inside the cap with a pump or the like to apply a sucking force (suction recovery, U.S. Pat. No. 6,722,757). 
As described above, it is possible to reduce bubbles remaining in the liquid chambers by suction recovery; however, conventional recording heads need frequent suction recovery, thus posing the problem of wasting ink every suction recovery, so that it cannot be used for recording.
A possible method for solving the problem is to reduce the frequency of suction recovery by increasing the liquid-chamber width W so as to prevent bubbles from staying in the liquid chambers so that the presence of bubbles in the liquid chambers does not easily exert a bad influence on recording. However, as shown in FIG. 16B, the liquid chambers H2201 to H2203 are arranged parallel in correspondence with the ink supply ports H1102, so that the width W (FIG. 16C) of at least the inner liquid chamber H2201 cannot be increased because of the presence of the other liquid chambers H2202 and H2203 on either side. Another possible method is to increase the liquid-chamber width W by increasing the distance between the ink supply ports H1102. This is, however, not desirable, because this increases the area of the recording element substrate, thus increasing the cost.
Meanwhile, a thorough examination on generation and growth of bubbles in liquid chambers showed that bubbles B exhibit the behavior shown in FIGS. 17A to 17F. That is,  the bubbles B are generated at the ends of the liquid chambers (FIG. 17A), continue to grow while staying at the ends (FIGS. 17B to 17D), quickly move toward the communicating portion C due to vibrations or the like (FIG. 17E), and at the communication part C, the ink flow is substantially blocked (FIG. 17F). Vibrations are generated when the recording head is mounted or the ink tank is mounted.
A possible method for solving such problems is to increase the x-direction length Cx (FIG. 16A) of the communicating portion C so that the ink flow is not blocked at the communicating portion C. However, as shown in FIGS. 16B and 16C, the inner ink supply path S01 cannot sometimes have sufficient Cx because of limitations due to the positional relationship among the ink supply paths S01 to S03.